1. Field of the Invention
The invention relates to a method of printing an object on a support, said object having a surface of varying height, by a printer configured to print a sequence of pass images on top of each other in a number of passes. Furthermore, the invention relates to a print system, in particular an ink jet print system, for printing an object on a support, said object having a surface of varying height, the print system being configured to print a sequence of pass images on top of each other in a number of passes. The term “printing” or “print” refers to building an object from print material by additive manufacturing, and includes, in particular, jetting print material for depositing the print material on the support or an already printed portion of the object.
2. Description of the Related Art
Recently, print systems have been developed that allow to print multilayer structures that can reach a considerable height as compared to conventionally printed images that are basically flat, or, at least, the height of which is generally disregarded. The structures are generated by stacking layers of material on top of each other. For example, radiation curable ink, in particular UV curable ink, may be used. By repeatedly printing a layer on top of a previously printed, cured layer, a multilayer structure may be built up having a defined height. For example, the height may be up to 10 mm or more. The height, i.e. the thickness of the printed structures, adds an extension in a further dimension to the two dimensional image, and, accordingly, such prints are termed 2.5D prints or relief prints. The printed structure may comprise an image, e.g. a color image.
U.S. Pat. No. 8,976,415 describes a method for generating relief prints, including processing a relief image, comprising color channels for indicating a color of each pixel and a height channel for indicating a height of each pixel, into several passes that are printed using a printer with several colorants including a white colorant. For each pixel a relief part, a white part and a skin part are discriminated. A height variation of individual pixels is caused by repetitive printing of colorants in the relief part. A number of pass images are derived from the relief image to be printed on top of each other. All available colorants may be used in the relief part, in order to provide for an optimal print speed for this part. The skin part comprises pass pixels for which a colorant composition based on the color channels of the relief image is established.
For printing relief prints or 3D prints, an object is built by stacking layers of material on top of each other. A slicing technique is known that consists in decomposing the object into a set of horizontal layers, which are printed on top of each other.
It is an object of the invention to provide a system and method that facilitate fast printing of relief prints or 3D prints with high surface quality or, in general, enhanced visual print quality of a relief or 3D printed object.